<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="../css/demo1.css">
</head>

<body>
    <div id="app">
        <div class="main">
            <img src="../image/main1.JPG" alt="">
            <img src="../image/main2.JPG" alt="">
            <img src="../image/main3.JPG" alt="">
        </div>

        <div class="adv">
            <img src="../image/adv.jpg" alt="">
        </div>
        <div class="toTop">
            回到<br />顶端
        </div>
    </div>
</body>
<script>
    //
    let adv = document.querySelector('.adv')
</script>

</html>